Hydrated Lime Mix for Exterior Wall Plaster — 6 Comments

  1. Hello,
    I am in the process of mixing water, DRY hydrated lime powder and fine sand for interior wall plaster inn old house.
    Your recipe states

    ” mix that best worked for us for outdoor wall plaster is a ratio 3x sand to 1x lime..”

    Now sand is MUCH heavier than the powder lime. So I inquire of you:
    Do you mean parts by WEIGHT, or parts by VOLUME ?

    I am guessing weight, since three times the volume of the lime for the sand seems out of bounds.
    – John

  2. Hi Owen,

    This seems like a really sturdy example of a lime plaster, and I’m considering this as an external plaster for our house. In your opinion, if I were to use a magnesium cement mix-in instead of what I’m assuming here was portland cement, would it perform in the same way (though better, given MgO cement’s superior qualities)? Since MgO cement tends to set much faster, would it make the drying time too fast to be workable? If you think this route is worth pursuing, I plan to perform some experiments.

    If there’s a better plaster option in our climate (mostly mild, with hot summers, occasionally sub-freezing winters, and fairly humid at times throughout the year), especially if I could use MgO cement in it (or a completely earthen mix, perhaps stabilized with lime), I’d appreciate the suggestion.

    Thanks so much!


  3. Interesting topic “Painting Earthbags”. We at times paint our Earthbags with a Lime paint. In our part 2 Video we show our “Air Tower” where we only applied a protective Lime paint layer. It did not hold up under our rainy seasons and vast parts blistered or ripped off as can be seen on this part 2 Video.

  4. I was wondering, if you simply paint the earthbags, would they still deteriorate? I understand they wouldn’t be protected from tears and such.

    • Polypropylene bags can last for centuries if protected from sunlight. So yeah, paint the bags and they should last a very long time. This is best for large jobs or where the project will take a long time until the walls are plastered.

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